Evolution of the total ionizing emissivity. The red, black, and green squares are our estimations after integrating from M_UV = −23 to M_UV = −13, M_UV = −15, and M_UV = −18, respectively. The black and green squares are shifted by 0.1 and 0.2 in redshift, respectively, for better visualization. The different lines represent IGM evolution models from Madau et al. (1999) for different ionized hydrogen clumping factors C. The blue squares are observational constraints obtained by observing the Lyα forest from Becker & Bolton (2013).